In the beginning, rock 'n' roll in the United Kingdom was inspired by the blues, country and pop music being invented in its former American colony.

Which was only fair and logical. Most of American traditional music - folk, country, bluegrass - had originated in vintage styles from the U.K. and other Celtic countries.

However, Mumford & Sons - four guys from London - are the first English group to gain legitimate mainstream success in the U.S. by reversing the spin.

Incorporating accordion, banjo, mandolin, resonator guitar and horns, Marcus Mumford and friends added an English accent to what's now known as "Americana" music, once known as folk-rock.

In 2012, "Babel," their second album, made it to No. 1 here. They sold out shows at major shrines such as the Hollywood Bowl and smaller venues in musical outposts rarely reached by American bands.

Though the interplay - which once was intense and creatively inspiring - is increasing, there's still a distinct oceanic divide detectable.

Some U.K. and Scandinavian examples from 2012 that are worthy of any era or level of cross-pollination:

"The 2nd Line" by Muse: This trio from Teignmouth, Devon, England, continues to mix a thundering hard-rock essence with grandiose themes and songscapes voicing outrage at a world of avarice and alienation. With hints of sci-fi spookiness. Unfortunately, mighty guitarist Matthew Bellamy's impassioned vocals are missing on two spacey songs sung without any particular distinction by bassist Christopher Westenholme.

"Strangeland" by Keane: Across a generous 16 songs, this quartet from Battle, East Sussex, England, sticks to what it does best. Tom Chaplin's vulnerable vocals complement melodic, tuneful songs detailing the hopes, disappointments, joys and letdowns of relationships ("You've got time to realize you're shielded by the hands of love").

"Come of Age" by the Vaccines: Though album No. 2 from this West London foursome doesn't quite smash and bash with as much unbridled punk spirit as its 2011 debut, it still charges youthfully ahead in the vein of Arctic Monkeys and the Libertines.

"Django Django" by Django Django: This Edinburg, Scotland, quartet's debut echoes with 1980s synth-pop hints not unlike fellow Scots Franz Ferdinand. Clever bits of percussion and odd sounds and effects keep it intriguing. (The name has nothing to do with Django Reinhardt or the movie "Django Unchained.")

"Rebirth" by Jimmy Cliff: A pioneer of Jamaican reggae, Cliff, 64, expanded on a 2011 EP, demonstrating his voice has lost none of its substance or sweetness. Produced by Tim Armstrong of Berkeley's Rancid, it's a supple, soulful sample of Cliff's greatness as he covers the Clash ("Guns of Brixton") and Rancid ("Ruby Soho") while continuing to wearily observe injustice and inhumanity's global persistence.

"Coexist" by The xx: It doesn't get much darker or dreamier than this. The music evolves slowly and softly with a slightly sinister sentiment. Romy Madley Croft and Oliver Sim sing mostly about the perils of relationships - "We used to be closer than this/Is it something you miss?" - with assists from guitarist Oliver Sim.

"Babel" by Mumford & Sons: Marcus Mumford, Winston "Country" Marshall, Ben Lovett and Ted Dwane continue careening and carousing - with a few introspective lamentations, too - through Celtic-tinged folk-rock, proving they're no one-hit wonder like Scotland's Proclaimers. Mumford's vocals get after it with total conviction - with occasional, growly bitterness ("you cut me dow-ow-ow-ow-ow-n") - as his bandmates churn away with fiery spirit. It's amazing that a banjo-plucking band is being accepted so widely.

"My Head Is An Animal" by Of Monsters And Men: Worthy of the Bjork and Sigur Ros, this five-piece band from Gardur, Iceland, constructs dramatic guitar anthems with chanting choruses clearly in the spirit of Montreal's Arcade Fire. Nanna Bryndís Hilmarsdóttir mixes child-like charm with wild wonderment on tunes full of mystery, magic and ancient allegory. Ragnar Borhallsson balances her with relative bemusement as the music rings, chimes and churns

"Sugaring Season" by Beth Orton: She doesn't release albums very frequently - this is Orton's first since 2006 - but Orton, 42, originally from East Dereham, Norfolk, England, always re-asserts her status as one of her country's most incisive, insightful and engaging singer-songwriters. Her flexibly expressive voice - alternately soaring, confessional and dusky - evokes traditional English styles framed by a kind of chamber-rock ensemble. With some jazzy-bluesy bits, too.

"Halcyon" by Ellie Goulding: This 26-year-old singer-songwriter from Lyonshall, Herefordshire, England, sings in a sweetly girlish style - unlike recent British soul-based powerhouses (Adele, Florence Welch and the late Amy Winehouse). That doesn't decrease the dramatics or dynamics. On her second album, Goulding demonstrates she could be next.

Some others: "Bish Bosch" by Scott Walker; "Beacon" by Two Door Cinema Club; "Rhythm & Repose" by Glen Hansard; "Rooms Filled With Light" by Fanfarlo; "Fallen Empires" by Snow Patrol; "How About I Be Me (and you be you)?"; "Observator" by the Raveonettes; "Shrines" by Purity Ring; "The Lion's Roar" by First Aid Kit; "Standing at the Sky's Edge" by Richard Hawley; "Lonerism" by Tame Impala.